Ultra compact optical fiber Fabry-Perot interferometer based on in-line integrated sub-micron silicon film

In this work, an ultra compact in line fiber optic Fabry-Perot interferometer is presented. The interferometric structure consists of a thin (< 1 mu m) amorphous silicon layer in line integrated into a standard single mode optical fiber by means of an electric arc discharge technique. The device exhibits low loss (1.46 dB) and high interference fringe visibility (similar to 30% in linear scale) both in reflection and transmission due to the high refractive index contrast between silica and alpha-Si. A high linear temperature sensitivity up to 75 pm/degrees C is demonstrated in the range 15-52 degrees C. The proposed device is simple, compact, cost effective and attractive for point monitoring sensing application in ultra-high temperature sensing in harsh environments.